Within the art of chip removing or cutting machining of workpieces of metal, there have recently been developed a number of interfaces between the basic body of the tool and the individual cutting insert, more precisely, in the form of varying topographies of the two connecting surfaces engaging mechanically in each other. An object of these modern interfaces is to allow the use of directly pressed, i.e., unground cutting inserts, without minor form defects in the same jeopardizing the machining precision of the tools. Contrary to the older tools, which make use of surface contact between simple, plane bottom and side surfaces in a ground cutting insert as well as a machined insert seat, more modern cutting tools are formed with interfaces in which a plurality of pair-wise co-operating male and female elements are included. Originally, these elements were constituted of a plurality of long narrow parallel and cross-sectionally wedge-shaped ridges and grooves, which together formed so-called serration connecting surfaces. Later, the interfaces have been developed so that certain pairs of ridges/grooves are transverse in relation to others in order to, in such a way, lock the cutting insert in two coordinate directions perpendicular to each other. In addition, interfaces have been produced, the male and female elements of which are no longer elongate, but are in the form of knobs and seatings without any marked length extension.
Common to previously known interfaces, irrespective of whether the male and the female elements are elongate or not, is that the absorption of the cutting forces (axial, radial, and tangential, respectively) is effected by contact between on one hand converging flanks of the male elements and on the other hand diverging flanks of the female elements, the contact between the flanks usually being limited to a line and/or point contact, rather than being a surface contact. Such interfaces may in practice give an acceptable transfer of force in two coordinate directions, but not simultaneously in a third. In, for instance, milling cutters, the axial and radial forces acting on the cutting insert are carried in a satisfying way, while the tangential forces, which aim at pressing in the male and the female elements into each other, are only carried by line or point contact. This involves, among other things, a risk that the cutting insert is dislodged from the exact space position thereof in the basic body of the tool. Generally, the more contact surfaces that should co-operate in an interface, the greater becomes the risk that possible form defects in the cutting insert are added to each other and result in an erroneous, unstable fixation of the cutting insert.
Tools of the kind in question are disclosed in U.S. Pat. Nos. 6,619,892; 5,944,456; 6,146,061; and 6,840,716, for example.
U.S. Pat. No. 6,203,251 discloses a cutting tool in the form of a milling cutter, the basic body of which is formed with an insert seat in which an elevation or head is included, which engages a depression in the underside of the individual cutting insert. However, in this case, there are no internal shoulder surfaces adjacent to the depression pressed against side support surfaces of the elevation. On the contrary, external contact surfaces of the cutting insert are pressed against side support surfaces that are spaced apart from the elevation. This means that possible form defects of the cutting insert will propagate all the way through the same and in such a way impair the machining precision of the tool.
The present invention aims at obviating the above-mentioned shortcomings of previously known cutting tools, and at providing a cutting tool having an improved interface between the basic body and cutting inserts of the tool. Therefore, an object of the invention is to provide a tool having an interface, which includes a minimum number of co-operating contact surfaces, and which, in spite of this, ensures good absorption of the cutting forces in all three coordinate directions.
Another object of the invention is to provide a tool interface, the two co-operating connecting surfaces of which can be manufactured in a simple and reliable way. Thus, the cutting insert, usually composed of cemented carbide, may be produced by conventional compression moulding and sintering without necessarily needing to be precision ground before use. Furthermore, the basic body may be formed with connecting surfaces by simple machining, such as milling and/or drilling.
Yet another object of the invention is to provide a cutting tool, the cutting inserts of which can be mounted in the appurtenant insert seats in the basic body in a smooth way for the operator, even if the cutting inserts are very small.